BALTIMORE -- Two weeks ago, Steve Pearce was wearing a Scranton/Wilkes-Barre uniform -- the New York Yankees' Triple-A affiliate -- and dealing with long bus rides while playing in front of half-filled stadiums.

On Thursday, Pearce had a career-high five RBIs, blasting his first homer in more than a year and electrifying the crowd of 29,995 at Camden Yards as the Orioles stormed to a 12-6 win against his former club, the Pittsburgh Pirates.

Crazy? Unpredictable? Welcome to the O's 2012 season.

Arguably the biggest surprise in baseball over the season's first two-and-a-half months, Baltimore kept rolling with a three-game sweep over Pittsburgh for its fifth consecutive win, equaling the O's longest streak of the year.

"It is nice playing against the Pirates," said Pearce, his Pittsburgh equipment bag packed in a box to his right as he discussed one of the highlights of his career. "This is definitely a great night for myself, personally."

It was a pretty good one for the rest of the Orioles, too.

Baltimore has won three consecutive series and is now one-half game back of the Yankees for first place in the American League East. Buoyed by Pearce and Matt Wieters -- who had a five-RBI night of his own -- the O's put forth their largest offensive output of the season with new season highs in runs scored, hits (16) and doubles (eight).

142 wins

110 wins

After a four-run outburst in the first inning -- that included three straight two-out hits -- Pearce pushed the O's into double-digits with a three-run homer off reliever Doug Slaten in the sixth. The blast, Pearce's first Major League homer since May 25, 2011, capped a five-run frame and was the kind of unexpected performance that has been business as usual for this Orioles club.

Consider this: Pearce had 10 RBIs in 50 games for the Pirates last season, and now has eight in his first seven with Baltimore. The 29-year-old has played parts of five prior seasons in the Majors and has never had more than 16 RBIs in a season. But with injuries to outfielders Nick Markakis, Nolan Reimold and Endy Chavez, Pearce has been given an opportunity. And so far, he has run with it.

"Steve's coming up here and letting it rip," said manager Buck Showalter, "and trying to find a spot and trying to make it tough on us if we get some of these people back."

"These guys have been battling all year, coming off the bench," said Chris Davis, who went 2-for-4, of an Orioles club that has gotten a lift from its reserves numerous times this season.

"It's not an easy thing to do, knowing you're not going to be in there every day, but knowing that there's a good chance you might have to step up," Davis added. It's huge for those guys to get in there and really give us a boost off the bench. We've got a lot of guys who can do that."

Pearce was front in center in Thursday's win, but he is hardly the only one stepping up, as Wieters had an outstanding night and Mark Reynolds continues to show signs of putting it together at the plate, going 4-for-5 with a homer, two RBIs and three runs scored.

"The guys put some good at-bats together early and we were able to get on base," said Wieters, who has 18 hits in his last 49 at-bats after going 3-for-42 prior to that run.

"That's all [in the] past. When you're playing well, you have to try and rack up as many wins as you can."

Orioles starter Tommy Hunter picked up his first victory since April 24 against Toronto. The right-hander was dominant early, retiring the first 12 batters he faced on an impressive 35 pitches. But Hunter couldn't sustain his success, allowing a pair of singles in the fifth and Rod Barajas' three-run homer to ruin any shutout hopes.

"I still have things to work on," said Hunter, who allowed five runs over six innings.

"I actually felt really strong today. It [stinks] to say that's the best you felt and turn around and see five runs on the board. But that's the way it is going to go sometimes. Just take those first four innings and take them into your next start. And then go."

Baltimore wasted little time getting to Pirates starter -- and former Oriole -- Erik Bedard, scoring four runs in the first inning, the most by the O's to start a game this season. Bedard struggled in an abbreviated start, exiting after 3 1/3 innings to mark his shortest non-injury outing this season.

"I mean they were hitting good pitches, they were hitting bad pitches," Bedard said of his 87-pitch outing. "They pretty much were hitting everything. It was just one of those games."

Thursday's win marked the Orioles' first three-game sweep at home since April 24-26 versus Toronto and improved them to 7-2 in Interleague Play this year, matching their total in wins against the National League from 2011.

Since Interleague Play began, Baltimore has the lowest win total of any American League club. It also marked just the second time in club history the team has had two players with five or more RBIs in a game, with Cal Ripken (six) and Will Clark (five) also accomplishing the feat on June 13, 1999.

"It felt good, I'll tell you that," Pearce said of his night at the plate. "It's just great having everybody hitting. It's contagious. Everybody just wants to get to the plate and tonight was one of those nights again."